1. Field of the Invention
This invention relates to an air filter assembly and, more particularly to an air filter assembly which is provided, for example, at an air inlet portion of a valve for use in an exhaust emission cleaning system.
2. Description of the Prior Art
In conventional exhaust gas emission systems, a vacuum switching valve, a vacuum control valve and other related valves are utilized. One or more of these valves are known as air-breathing type valves. The air-breathing type valve is designed to let air be introduced therein simultaneously with the valve opening thereof for alternating signal pressure.
In order to let air be introduced into the air-breathing type valve, a hose connected with an air-cleaner is frequently used with the result of the entire exhaust emission system being complicated in construction.
For this reason, recent vacuum switching valves, vacuum control valves and other related valves are provided with an air inlet port to let air be introduced therein at the housing thereof with the air filter being incorporated in the housing.
Therefore, the valves cannot be simple in construction and it is not easy to incorporate an air filter into the housing or to replace or change the air filter.
In consideration of the above-noted circumstances, there has been provided an air filter assembly which can be provided at an air inlet pipe portion for connecting with the housing in a single action.
However, the conventional air filter cases of this type have drawbacks in assembly thereof and replacing the air filter because the filter case and filter cap are separately formed.